I'm working on a potting mix for interior plants. And I want it to hold very little water and it should have great aeration and drainage.
I'm looking for a material (organic/inorganic) that is cheap and in the right granulometry to use as at least 60% of my potting mix. I'll provide the nutrients through fertilization if necessary (if it's an inorganic material, for example).
I see that bonsai folks use turface, but that is not so easy to find and when it's sold as "bolsai soil" it's really expensive.
What would be a good option in this case?